The overall objective of this proposal is to continue studies aimed at developing new information on the molecular basis of contraction and its control in cardiac and various types of skeletal muscle. Proteins of the contractile (myosin and actin) and regulatory (troponin, tropomyosin) machinery will be characterized by chemical, physico-chemical and enzymatic methods. The interactions of the relevant proteins with each other and with metal ions, in particular with Ca2+, lanthanides and nucleotides will be investigated with a view to obtaining a better insight into the process of mechano-chemical transduction and Ca2+ dependent regulation in vivo. Efforts will be made to relate chemical features of the part of myosin which contains the nucleotide and actin binding sites to dynamic (motional) aspects, which in turn are likely to underlie the cyclic mechanism of actin-myosin interaction. The Ca2+ dependent regulatory process will be studied by focusing on troponin and its subunits and their interaction with each other and the contractile system. The interaction with Ca2+ will be studied by direct binding and with the use of various spectroscopic probes. Studies will be continued on the mechanism of activity induced transformation in skeletal muscle with the hope of gaining new insights into the process by which gene expression is changed. Preliminary results indicating the appearance of a new myosin subunit gene product will be followed up. One hopes that the results obtained in the course of this work will shed light not only on processes specific for normal and diseased muscle tissues but will be of interest in other complex systems involving multiple protein-protein interactions and regulatory processes.